i always run as admin and have no other user profile on my pc and all i dine between my first playthrough was a gpu driver update lol and other steam games portal1/2 bttf still work fine..
took a few secs but yay success !
THANKS 'Bilbo' baggins the corrupt
fancy that...but when i clsed the game and re tried back to the way it was ?!
did you do it with steam active or the game running ?
try restarting steam after the ticky boxy :P